System for determining a lens position

ABSTRACT

A system for determining lens position includes a first sensor component disposed on a stationary housing of a camera. A second sensor component is disposed on a rotating lens component of the camera. A processor is operatively connected to the first and second sensory components to identify the position of the rotating lens component of the camera based on a difference between a first angle defined by the first sensor component and Earth&#39;s gravitational field and a second angle defined by the second sensor component and Earth&#39;s gravitational field.

GOVERNMENT RIGHTS STATEMENT

This invention was made with government support under contract number HR0011-13-C-0068 awarded by Defense Advanced Research Projects Agency. The government has certain rights in the invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to optics, and more particularly to determining the lens position within a camera.

2. Description of Related Art

A variety of systems can be used to determine the position of a lens in an optical system. For example, in a typical consumer autofocus camera, an electrical motor can be used to move a lens and the control signals to the motor can be used to infer the final position of the lens. However, autofocus systems such as these can consume a relatively high amount of power, and can have limited accuracy.

Knowing the position of a lens in an optical system can be important in determining the distance to an object being imaged. One example of a use for knowing the distance to the object is for parallax correcting images taken from different viewpoints.

Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved systems and methods for determining lens position. The present disclosure provides a solution for this need.

SUMMARY OF THE INVENTION

A system for determining lens position includes a first sensor component disposed on a stationary housing of a camera. A second sensor component is disposed on a rotating lens component of the camera. A processor is operatively connected to the first and second sensory components to identify the position of the rotating lens component of the camera based on the difference between a first angle defined by the first sensor component and Earth's gravitational field and a second angle defined by the second sensor component and Earth's gravitational field. In certain embodiments, the system can include a second camera operatively connected to the processor such that the first camera can be a short wavelength infrared camera and the second camera can be a long wavelength infrared camera,

The system can further include a memory operatively connected to the processor. The memory can include program instructions to calculate a distance to a point of focus of the camera based on a position of the rotating lens component using the difference between the first and second angles. The memory can include instructions recorded thereon that, when read by the processor, cause the processor to parallax correct an image from the second camera based on the distance between the point of focus to the focal plane of the camera and the difference between the first and second angles.

A camera includes a housing and a lens rotatable relative to the housing. A first accelerometer sensor is disposed on the housing. A second accelerometer sensor is disposed on the rotating lens component. A processor is operatively connected to the first and second accelerometer sensors to identify the position of the rotating lens component of the camera based on a difference between a first angle defined by the first accelerometer sensor and Earth's gravitational field and a second angle defined by the second accelerometer sensor and Earth's gravitational field.

These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein:

FIG. 1 is a schematic of an exemplary embodiment of a system for determining lens position constructed in accordance with the present disclosure, showing first and second cameras;

FIG. 2 is a schematic view of the images received from the first and second cameras of FIG. 1, showing parallax;

FIG. 3 is a cutaway perspective view of a portion of the system of FIG. 1, showing sensor components disposed on the first camera;

FIG. 4 is a front schematic view of a portion of the system of FIG. 1, showing first and second angles; and

FIG. 5 is a front schematic view of a portion of a system of FIG. 1, showing the angle between an axis of the lens component and a sensor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an exemplary embodiment of a system for identifying lens position in accordance with the disclosure is shown in FIG. 1 and is designated generally by reference character 100. Other embodiments of systems in accordance with the disclosure, or aspects thereof, are provided in FIGS. 2-5, as will be described.

With reference to FIG. 1, a system 100 is shown that can determine the lens position of a first camera and electronically determine distance to a point of focus to correct parallax between multiple cameras. The point of focus of a lens system is controlled by moving a lens element or component relative to the image plane location using either a threaded barrel housing the lens system, a cam surface and a follower, or the like. The rotation of the lens system is directly translated into linear motion of the lens component along the optical axis, with respect to the image plane.

FIG. 1 illustrates overlapping fields of view 106, 108 of first and second cameras 102, 104 which are laterally spaced a constant distance apart relative to each other. The first and second cameras 102, 104 are spaced apart along a common plane. As will be understood by those skilled in the art, first and second cameras 102, 104 can be positioned relative to each other in any other suitable way. The first and second cameras 102, 104 can focus on objects 110, 112 a distance d1, d2, respectively, for displaying on a screen, for example, a heads-up display. The first camera 102 can be a short wavelength infrared camera (SWIR). The second camera 104 can be a long wave infrared camera (LWIR). The first and second cameras 102, 104 include a housing 120 (shown in FIG. 3) and a lens component 124 manually rotatable relative to the housing 120. Images displayed from the second camera 104 are altered to produce a parallax corrected composite image on a display screen including image information from both cameras 102, 104.

The term parallax as used herein includes the displacement due to separation between the optical axes. In other words, parallax is based on the separation between the two cameras. The parallax between first and the second images is further dependent on the distance to the object. Therefore, if the distance to the object is known, the parallax between the two images can be determined and used to adjust one or both of the images. For example, the pixels of one image may be translated to compensate for parallax. As such, a composite image showing features of both the SWIR camera 102 and the LWIR camera 104 can be produced with parallax correction so LWIR and SWIR features are properly aligned in the composite image. As will be understood, the parallax may differ for different parts of the images, if the distance to the imaged object or area varies within the image. The parallax may be determined for only one part of the image or independently for different parts of the image. If the parallax is determined for only one part of the image, this part can be determined in different ways. For example, the central portion of the image can be selected by default. As another example, it may be possible for an operator to select a portion of the image for which the parallax should be determined, for example, the portion containing an object of interest.

FIG. 2 schematically illustrates images produced by the first and second cameras 102, 104 of system 100 prior to correcting for parallax. First image portions 202, 212 imaged by the first camera 102 and second image portions 204, 214 imaged by the second camera 104, are taken of the same scene at the same time. Images 202 and 212 are essentially the same as images 204 and 214, respectively, but are slightly shifted with respect to each other because of the distance between the first and second cameras 102, 104. For simplicity, the objects shown are a circle 112 and a square 110. In FIG. 1, the circle 112 is farther away from the cameras 102, 104 than the square 110. Therefore, the displacement d2′ of the images of the squares 212, 214 is greater than the displacement d1′ of the images of the circles 202, 204. The pixels of images 204, 214 from the second camera 104 can be translated horizontally a distance d1′ and d2′ to create a composite image showing the features of the first and second cameras 102, 104 corrected for parallax.

In order to determine the distances d1′, d2′ required to translate pixels from the second camera 104, the respective distances dl and d2 to the objects 110, 112 from the first camera 102 must be determined. In the present disclosure, and as described in more detail below, the distances d1 and d2 to the point of focus 110, 112 of the first camera 102 are determined based on the rotatable lens component position when the first camera 102 is focused on objects 110, 112.

FIGS. 3 and 4 shows first camera 102 of system 100. System 100 for determining lens position is based on the axial position of the lens relative to the housing 120 of camera 102. A first sensor component 302 is disposed on the housing 120 of the first camera 102. A second sensor component 304 is disposed on the rotating lens component 124 of the first camera 102. The first and second sensors 302,304 are each operatively connected to a processor 130 (shown in FIG. 1). The sensor components 302, 304 can be accelerometer sensors, for example Microelectromechanical systems (MEMS). Rotation of the lens component 124 relative to the housing 120 causes the rotatable lens component 124 to move in a direction transverse to the housing 120 and closer to objects 110, 112. Once the rotatable lens component 124 is circumferentially rotated a desired distance to focus on objects 110, 112, the processor calculates a first angle α defined by the sensor component 302 and Earth's gravitational field. The processor next calculates a second angle β defined by the sensor component 304 and Earth's gravitational field. Once the first and second vectors are determined, the processor 130 calculates distances d1 and d2 from the first camera 102 based on a difference between the first and second angles α, β. More specifically, the difference between the first and second angles α, β. is used by the processor 130 to calculate the position of the rotatable lens component 124 with respect to the housing 120, which is used to infer distances d1 and d2 to the objects 110 and 112, respectively. In another embodiment, shown in FIG. 5, the angular measurement can be abbreviated by using only one angle. In this embodiment, the lens component 124 is used as the axis of rotation. An angle γ between rotating sensor 304 and the axis of the lens component 124 is used to infer distances d1 and d2.

It is contemplated that sensors 302 and 304 can be used in conjunction with the sensors shown and described in U.S. patent application Ser. Nos. 14/326,067 and 14/326,113 incorporated by reference in their entirety herein, to provide an even more accurate calculation of the position of rotatable lens component 124. Accordingly, magnetic sensor 306, shown in FIG. 3, may be used to further calculate the position of the rotatable lens 124. The advantage to using the Earth's gravitational field for measuring the distance to a point of focus is using it in conjunction with the magnetic sensor 306. Sensors 302 and 304 will experience distorted measurements if subjected to rapid and erratic motion, but are unaffected by nearby high-power electronics. The magnetic sensor 306, conversely, will experience distorted measurements when in the vicinity of high-power electronics, but will be unaffected by motion of the device. There are very few circumstances where the deficiencies of sensors 302,304 and magnetic sensor 306 overlap. Therefore, the combination of the two sensor types creates a more robust system.

In typical camera systems, the distance over which a lens system moves is extremely small relative to the very large shift in position of the point of focus. One degree of rotation could correspond to a very small translation in lens position. For example, one full rotation may move the lens system 0.5 mm. One degree of rotation would then correspond to 0.0014 mm, or 1.4 microns, of motion in the lens system. While it is very difficult to measure movement of only 1.4 microns, it is much simpler to measure one degree of rotation accurately.

The operation of processor 130 may be controlled with computer executable instructions, i.e., a program carrying instructions which can be executed by the processor. One or more memory units, here shown as memory 132, are operatively connected to the processor 130. The memory 132 is used to store computer executable instructions to be executed by the processor 130 when performing the functions of system 100 described herein.

With reference to FIG. 1, the second camera 104 is operatively connected to the processor 130. Once the processor 130 calculates the distances dl and d2, the processor 130 parallax corrects one or both images, for example, images 204 and 214. In other words, the pixels of the images 204 and 214 viewed from the second camera 104 are translated to align with the corresponding images 202 and 212 of the first camera 102. In this manner, a parallax corrected composite image including features from the first and second cameras 102 and 104 is shown on the display screen. This allows images in two different spectra, e.g., LWIR and SWIR, to be composited to show useful information from both.

The methods and systems of the present disclosure, as described above and shown in the drawings, provide for a system for identifying lens position with superior properties including correcting for parallax between two cameras based on the lens position. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the spirit and scope of the subject disclosure. 

What is claimed is:
 1. A system for determining lens position: a first sensor component disposed on a stationary housing of a camera; a second sensor component disposed on a rotating lens component of the camera; and a processor operatively connected to the first and second sensory components to identify the position of the rotating lens component of the camera based on a difference between a first angle defined by the first sensor component and Earth's gravitational field and a second angle defined by the second sensor component and Earth's gravitational field.
 2. The system of claim 1, further comprising a memory operatively connected to the processor including program instructions to calculate a distance to a point of focus of the camera based on the angle between the first and second vectors.
 3. The system of claim 2, further including a second camera operatively connected to the processor wherein the memory includes program instructions to transform an image from the second camera to align with an image from the camera.
 4. The system of claim 3, wherein the first camera is a short wavelength infrared camera.
 5. The system of claim 4, wherein the second camera is a long wavelength infrared camera.
 6. The system of claim 1, wherein the processor is operatively connected to a memory, wherein the memory includes instructions recorded thereon that, when read by the processor, cause the processor to: calculate a distance from a point of focus to a focal plane of a camera based on a position of the rotating lens component using the difference between the first and second angles.
 7. A system as recited in claim 6, wherein the memory includes instructions recorded thereon that, when read by the processor, cause the processor to: parallax correct an image from a second camera based on the distance between the point of focus to the focal plane of the camera and the difference between the first and second angles.
 8. A camera, comprising: a housing; a lens component rotatable relative to the housing; a first accelerometer sensor disposed on the housing; a second accelerometer sensor disposed on the lens; and a processor operatively connected to the first and second gravitational sensors to identify the position of the rotating lens component of the camera based on a difference between a first angle defined by the first accelerometer sensor and Earth's gravitational field and a second angle defined by the second accelerometer sensor and Earth's gravitational field.
 9. The camera of claim 8, further comprising a memory operatively connected to the processor including program instructions to calculate a distance to a point of focus of the camera based on the difference between the first and second angles.
 10. The camera of claim 9, further including a second camera operatively connected to the processor wherein the memory includes program instructions to transform an image from the second camera to align with an image from the camera.
 11. The camera of claim 10, wherein the camera is a short wavelength infrared camera.
 12. The camera of claim 11, wherein the second camera is a long wavelength infrared camera.
 13. The camera of claim 8, wherein the processor is operatively connected to a memory, wherein the memory includes instructions recorded thereon that, when read by the processor, cause the processor to: calculate a distance from a point of focus to a focal plane of a camera based on a position of the rotating lens component using the difference between the first and second angles.
 14. A camera as recited in claim 13, wherein the memory includes instructions recorded thereon that, when read by the processor, cause the processor to: parallax correct an image from a second camera based on the distance between the point of focus to the focal plane of the camera and the difference between the first and second angles. 